Although there is a fair choice of GUI libraries for Python (good overview of Python GUI libraries is here), sometimes we need just a little bit more enhanced terminal interface, like in my recent project – XMPP test client – where requirements were quite simple – just to split terminal screen into two areas – main screen where messages are displayed (possibly asynchronously) and bottom line, where commands/messages can be entered:
In Python we have couple of options for terminal UI programming:
- curses – curses library is part of standard python distribution, it provides lower level access to terminal programming and terminal control sequences. Many things are left to users – like resizing UI, event loops etc.
- urwid – is an excellent external library, which provides higher level interfaces for programming terminal UIs. It’s a bit similar to above mentioned GUI kits, providing widgets, layout managers, event loop etc. And many common tasks missing in curses are already included.
I decided to use urwid, because it looked easier to start with and many required functionalities were already provided (like already mentioned resizing, which I think would be pretty tedious to re-implement in curses). I’ve created simple commander module, which provides interface similar to build-in cmd.Cmd, but with UI layout as shown above. With this module we can create simple tools very easily:
if __name__=='__main__': class TestCmd(Command): def do_echo(self, *args): '''echo - Just echos all arguments''' return ' '.join(args) def do_raise(self, *args): raise Exception('Some Error') c=Commander('Test', cmd_cb=TestCmd()) #Test asynch output - e.g. comming from different thread import time def run(): while True: time.sleep(1) c.output('Tick', 'green') t=Thread(target=run) t.daemon=True t.start() #start main loop c.loop()
Which creates tool like this: